How to detect unknown compounds?

[xujing]

Hi,

I'm trying to know what compounds are in my sample. I've got GC-MS results. However, I'm still now sure what they are. Is there any other method(s) can help me to confirm the compounds? I read some article about detect unknow compounds with GC-MS and NMR. Can anyone please tell me if I can use this method or not?

Thank you very much!

[David Blais]

Do you at least know what classification of compounds (alcohols, esters, proteins)? Do you know how many different kinds there are in your sample? That will certainly help. You can use GC-MS and NMR to determine what is in your sample, but being able to narrow the number of possibilities would be a great benefit at the start.

[xujing]

Thank you very much for your reply!

Actually, I'm trying to find the decontamination pathways of phenanthrene by electric field. So, I don't know what the compounds are. I can't find any information about it from the literature.

I think we can get the molecular weight from GC-MS results.
NMR may help us with the carbon hydrogen framework.

I just got the GC-MS results. I don't actually know how to interpret the results. There are more than ten suggested names for each compound. So, I'd better check the mass spectrum first and try to find some clues. Then, try other methods, such as NMR, to confirm what they are.

Is this the right way to do it?

Thanks again!

[David Blais]

My somewhat limited experience with GC-MS and NMR tells me you are on the right path, but it will certainly be much harder with everything completely unknown. It certainly sounds like you are going about it the right way.

I'm not certain what types of NMR you have access to, but if you can get some 2D NMR tests completed, that would lend even greater confidence to your results. I would also look to find a textbook on fragmentation patterns in MS, they could likely have examples of what you are seeing. Or, if you have access to some type of MS library, that would be helpful, too.

I would also try to expand your literature search. While it's entirely possible that nothing has been documented on the decontamination pathways of phenanthrene, I would think there has to be something out there. Unless you are working in a completely new field of study. Since this is posted under "Student Projects" I assume you are working on your thesis or some research project. Perhaps your advisor/mentor can point you in a direction.

I hope this helps - good luck!